The present invention relates to a plasma processing apparatus, and particularly, to a high-frequency plasma processing apparatus of a magnetic-field assist type.
FIG. 10 shows a typical conventional plasma processing apparatus 1 of a magnetic-field assist type. The apparatus 1 comprises a processing chamber 10, an electrode 14 which serves as a mount base provided in the chamber 10, and a high-frequency power source 18 for applying a high-frequency voltage of a predetermined frequency to the electrode 14. In this structure, when a high-frequency voltage is applied to the electrode 14 by the high-frequency power source 18, a processing gas introduced into the processing chamber 10 is changed into plasma, thereby generating radicals and ions by which an etching processing (plasma processing) is performed on an object to be processed which is mounted on the electrode 14, for example. In this case, to achieve uniform etching, a permanent magnet 20 provided above the processing chamber 10 is rotated, to attempt to make uniform the plasma density over the entirety of a plasma formation region due to an effect of a magnetic field.
However, in the plasma processing apparatus shown in FIG. 10, the plasma density is the highest in the vicinity of inner walls of the processing chamber 10, due to so-called E.times.B drifting, so that it is difficult to obtain a uniform etching rate. In addition, a charge-up damage tends to easily occur due to deflection of plasma. This tendency is particularly outstanding under a low pressure. In the current situation in which high integration of integrated circuits has been promoted, a plasma source capable of generating high density plasma under a low pressure has been demanded and therefore, solution of the problem as described above has also been demanded. Further, it is difficult for the plasma processing apparatus shown in FIG. 10 to control the density distribution of plasma to be generated in compliance with processing conditions.